Abstract Powder neutron diffraction was used to investigate Zr₁₀Sc₄O₂₆, the so called γ-phase in the zirconia scandia system. This fluorite related anion deficient compound with composition MX_1.86 crystallizes in space group R-3 and lattice constants a = 952.7(3) pm and c = 1745.3(4) pm. Anion vacancies are inserted on the 6c sites in R-3. The neutron data as well as the periodic density-functional calculations performed count for a divacancy model. The paired defect is more stable by 29 kJ/mol than any model with unpaired vacancies including the model with the 1/2[111]_F (index F = fluorite) vacancy separation along an empty anion cube.